Sleep tight 

Basically sleep well and soundly. A cute goodnight message

Nighty night. Sleep tight.

Sleep tight by Letty Blue May 22, 2018

sleep tight 

Meaning Sleep well.
Very well used phrase in the English - speaking world. It's been common at bedtime for many years in the form of "good night, sleep tight, don't let the bedbugs bite", or something like that.

A: 'ight dude, I'm out. Good night.
B: Good night. Sleep tight.
A: Sweet! Thanks Brah!! I'll holler at you tomorrow. Peace out.
B: Peace.

sleep tight by Gnomster June 27, 2008

Sleep Tight Pupper 

Sleep Tight Pupper is a term used for Gabe the Dog or any popular dog meme on the internet, in which the dog is small, and usually indicates said pupper has passed.

Did you hear Gabe The Dog died.
Yeah... Everyone should say Sleep Tight Pupper before they sleep tonight.

Sleep Tight Pupper by Backtalkers February 5, 2017